- Cannabis Study: How THC Affects Learning and Memory at Different Ages
- Cannabinoids and Aging: What Did We Already Know?
- THC, Memory, and Aging Study: Basic Findings and Summary
- Cannabis and Aging: The Role of the Endocannabinoid System
- Study Caveat: Mice and Humans Metabolize Compounds Differently
- Study Caveat: Cannabis Was Not Consumed, Pure THC Was Administered
- Questions for Future Research
- The Future of Medical Cannabis Research: Which Countries Will Lead the Way?
- Piyanova A, Lomazzo E, Bindila L, et al. Age-related changes in the endocannabinoid system in the mouse hippocampus. Mech Ageing Dev. 2015;150:55-64
- Marijuana Side Effects & Symptoms of Abuse
- Article at a Glance:
- Signs of Marijuana Addiction
- Physical Symptoms of Marijuana Abuse
- Long-Term Health Effects of Marijuana Use
- Marijuana Overdose
- What You Need to Know About Marijuana Use in Teens
- Marijuana and the teen brain
- Negative effects on school and social life
Cannabis Study: How THC Affects Learning and Memory at Different Ages
“All diseases run into one, old age.” –Ralph Waldo Emerson
A recent study in mice sparked eye-catching headlines , “Memory Loss From Old Age Could Be Reversed By Smoking Marijuana.” The idea is alluring, especially given the toll cognitive decline takes as we age: instead of leaving you dazed and confused, THC might actually help restore cognitive function in older individuals.
While the study made interesting observations about how THC affects learning and memory in young vs. older mice, it didn’t involve smoking or cannabis consumption. What did the study find, how did it work, and what are the implications for future human research?
Cannabinoids and Aging: What Did We Already Know?
We knew three basic things going into this recent study. First, young mice have stronger learning and memory abilities than older mice—no surprise there.
Second, giving young mice THC generally makes them perform worse on learning and memory tests.
Third, the endocannabinoid system influences the progression of aging in the brain, and endocannabinoid levels in the brain decline with age.
Dr. Andras Bilkei-Gorzo, lead author of the recent study, explained the rationale for their experiments. “We had learned from previous work that decreased cannabinoid signaling accelerates brain aging. We asked whether enhancing cannabinoid system activity might slow down—or even reverse—normal cognitive decline that comes with aging.”
The idea was relatively straightforward. If age-related cognitive deficits are due, at least in part, to deficits in the endocannabinoid system, then perhaps exposure to a plant cannabinoid THC might compensate for this. So, how did their experiments work?
THC, Memory, and Aging Study: Basic Findings and Summary
The study looked at behavioral measures of learning and memory in young vs. old mice.
In each age group, some mice received a constant, daily dose of THC for 28 days, while others served as controls (they didn’t receive THC). After their 28-day treatment, their learning and memory abilities were assessed.
There was no THC in their system during assessment. The question was how learning and memory were affected after chronic THC exposure.
It turned out that old mice responded differently to chronic THC compared to young mice. Old mice did better on learning and memory tests if they had a 28-day THC treatment beforehand. The behavior of old mice that had a chronic THC treatment looked the behavior of young mice without a THC treatment.
There were also molecular changes in a brain area called the hippocampus that paralleled these behavioral changes.
Basically, the brains of older mice that had received THC looked more the brains of young mice without THC; there were more connections between neurons in the hippocampus. There were also some interesting genomic changes.
In the THC-treated old mice, genes associated with plasticity and extended lifespan were turned up, while genes associated with age-related cognitive impairment were turned down.
Figure 1: Chronic THC exposure in old mice can increase the number of connections between neurons in the brain. Brain cells often have structures called “spines.” Each spine marks a single connection between two brain cells.
Compared to young mice (left), neurons in old-mice (middle) tend to have fewer spines.
After chronic THC exposure (right), the brain cells of old mice often look more those of young mice–they have more spines, and therefore more connections to other brain cells.
Cannabis and Aging: The Role of the Endocannabinoid System
As we age, our endocannabinoid system changes, including changes in CB1 receptor levels.
CB1 is the receptor THC needs to activate for the classical effects of cannabis to be felt, and these receptor levels seem to generally decrease as we age.
Perhaps chronic THC exposure in old mice restored cognitive function by increasing CB1 activation, compensating for the low overall levels of CB1 receptors. Using genetically engineered mice, researchers found evidence consistent with this idea.
Figure 2: CB1 receptor levels decrease with age, and chronic THC exposure may compensate for this in old mice. Compared to young mice (top-left), old mice tend to have fewer CB1 receptors in their brain (top-right).
Because THC activates CB1 receptors, chronic exposure to low-dose THC may compensate for this age-related change in the endocannabinoid system. Each red “V” represents a CB1 receptor.
At any given time, some CB1 receptors may be activated (yellow lines) by cannabinoids, while others are not.
The broad takeaway from this study is that plant cannabinoids THC can have very different effects on individuals depending on their age. These differences are ly due to age-related changes in the endocannabinoid system. Elevating cannabinoids levels may help compensate for some of these age-related changes.
These results should remind us to be cautious about generalizing the results of studies conducted in specific age groups. We should also hesitate to generalize the results of animal studies to humans, as there are important differences in how our bodies process biologically active compounds.
Study Caveat: Mice and Humans Metabolize Compounds Differently
The study’s title is, “A chronic low dose of THC restores cognitive function in old mice.” But how low was the “low dose” that the mice received?
In this study, mice were given 3 milligrams per kilogram (mg/kg) of body weight of THC per day for 28 consecutive days before learning and memory assessments. For a 150-pound person, that would be equivalent to about 204 milligrams of THC.
Spread evenly throughout the day, that comes out to about 8.5 mg of THC every hour.
A standard THC edible in a legal adult-use state is 10 mg, so the dose these mice were getting would be akin to taking an edible every hour of every day, for an entire month.
While that’s far from a low dose for a human, mice are a different story. Dr. Bilkei-Gorzo explained, “Humans are much more sensitive to psychoactive substances than rodents.
The effective doses of anti-anxiety and anti-depression drugs is roughly 100 times higher in rodents compared to human patients.
The same is true for THC—one needs a higher dose in rodents to see effects comparable to humans.”
Rodents and humans metabolize plant cannabinoids, pharmaceuticals, and other compounds at different rates, and sometimes in very different ways. That’s one big reason why we need to careful about jumping to conclusions about how animal studies will translate to humans.
Study Caveat: Cannabis Was Not Consumed, Pure THC Was Administered
The mice in this study were given pure THC through small devices surgically implanted under their skin. This allowed THC to be directly administered at a constant rate.
Mice were not inhaling smoke or consuming cannabis products comparable to normal human consumption methods.
This is another reason why we should be cautious when thinking about how cannabis consumption will affect learning and memory in older humans.
Questions for Future Research
Despite these caveats, the results of the study are intriguing and illustrate how plant cannabinoids THC can have very different effects an individual’s age. These are ly due to age-related changes in the endocannabinoid system that unfold naturally over time. This points us to some important questions worth investigating in humans.
The first question is whether similar results would be seen in a human clinical trial. If so, would these results be seen after consumption of cannabis products through traditional consumption methods, or would older individuals need to acquire pure THC?
Thankfully, the researchers who conducted this animal study are designing experiments to investigate the effects of THC on elderly adults with mild cognitive impairment. “We are in the very beginning of the study design,” Dr.
Bilkei-Gorzo explained. “The best-case scenario is that the clinical trial will start at the end of 2017 or beginning of 2018. The human trials will most ly use THC.
This will allow us to precisely dose THC and compare the human results with the animal studies.”
While pure cannabinoid extracts are often used in human studies, there are legitimate reasons for why patients might respond differently to whole plant cannabis. “There are clear differences between cannabis and pure THC. Cannabis has the advantage of being better tolerated by patients, but pure THC can be precisely dosed.”
The Future of Medical Cannabis Research: Which Countries Will Lead the Way?
It’s also worth noting where the latest research is happening.
This recent study was led by researchers at the University of Bonn, in Germany, in collaboration with scientists at Hebrew University in Israel.
Israel has already established itself as the capital of medical cannabis research, while Germany and Canada are charging forward with federal legalization of medical and adult-use cannabis laws, respectively.
Meanwhile, federal prohibition in the United States means that medical cannabis research moves as slowly as possible. With the prospect of major budget cuts to government research agencies the NIH looming, countries Israel, Germany, and Canada may solidify themselves as the world’s medical cannabis research leaders, and be the first to reap the benefits.
Piyanova A, Lomazzo E, Bindila L, et al. Age-related changes in the endocannabinoid system in the mouse hippocampus. Mech Ageing Dev. 2015;150:55-64
Marijuana Side Effects & Symptoms of Abuse
Marijuana is a mind-altering drug that has several effects on the human body and mind. Using marijuana just one time can cause noticeable symptoms to appear. The longer a person uses it, the greater the risk for it to cause larger social changes in their life.
If you’re worried a friend or family member may be struggling with marijuana abuse or addiction, look for a combination of these signs, symptoms and side effects. Although they may try to hide their habit, these symptoms and signs are classic tells of marijuana use.
Article at a Glance:
- Marijuana can be habit-forming and has many effects on the mind and body.
- Signs of marijuana abuse are reduced mental and physical abilities, difficulties with work or school, social changes and troubles money or the law.
- Both physical and psychological symptoms can occur even after only using marijuana one time.
- Some long-term effects are chronic coughing, a drop in IQ, respiratory infections, mental health issues and addiction.
- Although there have been no documented fatal marijuana overdoses, nonfatal symptoms of an overdose include extreme paranoia, anxiety, hallucinations and anxiety.
Signs of Marijuana Addiction
As a person becomes more entrenched in marijuana use, you may start to notice a change in their priorities, behavior and social activity. This is because the feeling of getting high on marijuana seems enjoyable, so the person may prioritize getting high over other activities they were previously dedicated to.
Using marijuana (and ingesting THC) causes changes in the brain that may lead to additional changes in a person’s abilities and behavior over time. Some signs of marijuana abuse include:
- Social changes
- Employment or academic struggles
- Reduced cognitive and physical abilities
- Legal troubles
- Financial concerns
Social changes, for example, may include a disinterest in former hobbies or friends, partaking in risky behaviors, and a newfound interest in marijuana counterculture. For example, modern cannabis counterculture has an equally strong tie to the Rastafarian lifestyle; images of the marijuana leaf and Bob Marley are both commonly associated with marijuana counterculture.
Marijuana users may also engage in risky behavior. THC affects the frontal cortex, the part of the brain involved in decision-making, which may cause a person to make poor decisions.
As a result, a person may choose to drive a car while impaired or have unprotected sex while high.
By impairing one’s judgment, marijuana abuse can lead to an increased risk of contracting sexually-transmitted diseases HIV and AIDS.
Similar to how it affects judgment, THC may also affect a person’s physical abilities. A lack of coordination while high can cause a person to struggle while performing regular activities. This is also why driving while high on marijuana is unsafe — THC affects the cerebellum and basal ganglia, which are two parts of the brain that regulate coordination, balance, and movement.
Marijuana use also affects mental cognition or thinking abilities. This can be especially dangerous for adolescents, as studies have shown that smoking marijuana as an adolescent can reduce a person’s IQ permanently. Some signs a teen may be abusing marijuana include failing grades, reports of skipping classes or not earning the grades to graduate on time.
Financial and legal troubles also go hand-in-hand with marijuana abuse. If someone gets caught selling or using the drug without a prescription, they could be arrested and face jail time, resulting in costly attorney fees and bail payment.
Physical Symptoms of Marijuana Abuse
When a person ingests cannabis, the drug releases THC (tetrahydrocannabinol) in the brain. This mind-altering chemical causes several effects, which may result in a person experiencing physical and psychological symptoms. These effects can occur in the short-term, even after one instance of marijuana use.
It’s not uncommon for people to also experience heart attacks following marijuana use, especially when it has a more potent concentration of THC. A person’s risk of heart attack can increase up to five times within the first hour after smoking marijuana. This is because it raises blood pressure and heart rate while reducing the blood’s ability to carry oxygen.
Signs of a heart attack include chest pain, lightheadedness, nausea or vomiting, neck, jaw or back pain, shoulder or arm pain, and shortness of breath.
A heart attack can be fatal and is a medical emergency. If you see someone experiencing the signs of a heart attack, call 911 immediately.
Long-Term Health Effects of Marijuana Use
The longer a person uses marijuana, the more exposed they are to THC and its effects. Over time, marijuana abuse can lead to the development of many dangerous conditions and adverse health effects.
Long-term side effects of marijuana use include:
Scientists have been doing significant amounts of research on how cannabis use affects mental capacity.
For example, a recent Duke University study in New Zealand revealed that people who heavily smoked marijuana in their adolescent years and later became addicted to the drug lost eight IQ points between ages 13 and 38.
Sometimes, the long-term effects of drug abuse can be repaired over time as the brain has a chance to heal in sobriety. However, this study showed these individuals did not regain their IQ points after they stopped using marijuana.
For women of childbearing age, marijuana use can also negatively impact pregnancy and unborn children. Using marijuana while pregnant has been known to cause low birth weight and an increased risk of stillbirth. Marijuana use during pregnancy has also been linked to brain damage in the developing fetus. Children born with prenatal marijuana exposure have shown:
- Attention problems
- Memory problems
- Difficulty with problem-solving skills
Some preliminary research also shows that postpartum marijuana use can lead to an accumulation of THC in breast milk. If a nursing mother repeatedly uses marijuana, the THC levels in their breast milk could reach a high enough level to stunt brain development in their baby.
When a person ingests too much marijuana, an overdose (essentially drug poisoning) occurs. While overdose is commonly fatal with other drugs, there are no reports of a fatal overdose on marijuana alone.
You may have had a nonfatal marijuana overdose if you experienced these symptoms:
- Extreme hallucinations
- Extreme anxiety
- Extreme paranoia
It’s possible to experience overdose on any form of marijuana, but it’s particularly ly when eating marijuana edibles.
This often occurs because inexperienced edible users don’t realize how long it takes to feel the effects of the drug and eat an increased dose.
This is more ly to occur with teenagers who have never taken edibles before, or even with small children who eat an edible without knowing it contains cannabis.
Although the overdose is typically nonfatal, it may be important to treat the overdose as a medical emergency and seek immediate medical treatment. One can visit their doctor’s office or a hospital right away. If you believe the person who has overdosed may harm themselves or others, it may be best to call 911 and let emergency personnel handle the situation.
If you or a loved one is struggling with marijuana use or addiction, The Recovery Village can help. Contact us today to learn more about treatment options and plans that can work well for your situation.
- SourcesAmerican Heart Association. “Heart Attack and Stroke Symptoms.” Accessed June 25, 2020.National Institute on Drug Abuse. “Commonly Abused Drugs Charts.” Accessed June 25, 2020.National Institute on Drug Abuse. “DrugFacts: Marijuana.” December 19, 2020. Accessed June 25, 2020.National Institute on Drug Abuse. “Marijuana.” May 12, 2020. Accessed June 25, 2020.American Medical Association. “AMA Applauds Surgeon General’s Advisory on Cannabis.” August 29, 2019. Accessed June 19, 2020.National Institute on Drug Abuse. “Marijuana Research Report.” April 2020. Accessed June 19, 2020.Duke University. “Adolescent Pot Use Leaves Lasting Mental Deficits.” August 27, 2012. Accessed July 7, 2020.
Medical Disclaimer: The Recovery Village aims to improve the quality of life for people struggling with a substance use or mental health disorder with fact-based content about the nature of behavioral health conditions, treatment options and their related outcomes.
We publish material that is researched, cited, edited and reviewed by licensed medical professionals. The information we provide is not intended to be a substitute for professional medical advice, diagnosis or treatment.
It should not be used in place of the advice of your physician or other qualified healthcare provider.
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What You Need to Know About Marijuana Use in Teens
- 38% of high school students report having used marijuana in their life.1
- Research shows that marijuana use can have permanent effects on
the developing brain when use begins in adolescence, especially with regular or heavy use.2
- Frequent or long-term marijuana
use is linked to school
dropout and lower educational achievement.3
The teen years are a time of rapid growth, exploration, and onset of risk taking. Taking risks with new behaviors provides kids and teens the opportunity to test their skills and abilities and discover who they are. But, some risk behaviors—such as using marijuana—can have harmful and long-lasting effects on a teen’s health and well-being.
Marijuana and the teen brain
Un adults, the teen brain is actively developing and often will not be fully developed until the mid 20s. Marijuana use during this period may harm the developing teen brain.
Negative effects include:
- Difficulty thinking and problem solving.
- Problems with memory and learning.
- Impaired coordination.
- Difficulty maintaining attention.3
Negative effects on school and social life
Marijuana use in adolescence or early adulthood can have a serious impact on a teen’s life.
- Decline in school performance. Students who smoke marijuana may get lower grades and may more ly to drop high school than their peers who do not use.4
- Increased risk of mental health issues. Marijuana use has been linked to a range of mental health problems in teens such as depression or anxiety.5 Psychosis has also been seen in teens at higher risk those with a family history.6
- Impaired driving. Driving while impaired by any substance, including marijuana, is dangerous. Marijuana negatively affects a number of skills required for safe driving, such as reaction time, coordination, and concentration.7, 8
- Potential for addiction.a Research shows that about 1 in 6 teens who repeatedly use marijuana can become addicted, which means that they may make unsuccessful efforts to quit using marijuana or may give up important activities with friends and family in favor of using marijuana.
a The term “addiction” is used to describe compulsive drug seeking despite negative consequences.
However, we recognize that “addiction” is not considered a specific diagnosis in the fifth edition of The Diagnostic and Statistical Manual of Mental Disorders (DSM-5)—a diagnostic manual used by clinicians that contains descriptions and symptoms of all mental disorders classified by the American Psychiatric Association (APA). Rather the DSM-5 uses the term substance use disorder. However, throughout this document addiction is used synonymously with having a substance use disorder for ease of language recognition and understanding.
- Centers for Disease Control and Prevention (CDC), High School Youth Risk Behavior Survey Data. 2016 [cited 2016 November 16, 2016]; Available from: http://nccd.cdc.gov/youthonline/.
- National Institute on Drug Abuse. What are marijuana’s long-term effects on the brain? 2016 [cited 2016 November 16, 2016]; Available from: https://www.drugabuse.gov/publications/marijuana/what-are-marijuanas-long-term-effects-brainexternal icon.
- Fergusson, D.M. and J.M. Boden, Cannabis use and later life outcomes. Addiction, 2008. 103(6): p. 969-76; discussion 977-8.
- Broyd, S.J., et al., Acute and Chronic Effects of Cannabinoids on Human Cognition-A Systematic Review. Biol Psychiatry, 2016. 79(7): p. 557-67.
- Copeland, J., S. Rooke, and W. Swift, Changes in cannabis use among young people: impact on mental health. Curr Opin Psychiatry, 2013. 26(4): p. 325-9.
- Arseneault, L., et al., Cannabis use in adolescence and risk for adult psychosis: longitudinal prospective study. BMJ, 2002. 325(7374): p. 1212-3.
- Bondallaz, P., et al., Cannabis and its effects on driving skills. Forensic Sci Int, 2016. 268: p.92-102.
- Hartman, R.L. and M.A. Huestis, Cannabis effects on driving skills. Clin Chem, 2013. 59(3): p. 478-92.
- National Institute on Drug Abuse. Drugs, Brains, and Behavior: The Science of Addiction 2014 [cited 2016 December 29].